JP2010233131A - Wireless communication device and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication device and a wireless communication method for suppressing reduction in throughput by reducing communication error rate on a wireless communication path provided between wireless communication devices. <P>SOLUTION: The wireless communication device (e.g., a gateway station 1) measures communication error rate on a wireless communication path (20a) between the device (the gateway station 1) and another wireless communication device (e.g., a relay station 2A). When the measured communication error rate exceeds a predetermined threshold, the wireless communication device (the gateway station 1) selects a new frequency channel which is set and changed on the wireless communication path (20a). Thereafter, the wireless communication device (the gateway station 1) transmits information about the new frequency channel via a wireless communication path (20b, 20d) different from the wireless communication path (20a) to another wireless communication device (the relay station 2A), and sets and changes the frequency channel of the wireless communication path (20a) to a new frequency channel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method.

  2. Description of the Related Art In recent years, wireless communication devices have been widely used in various places as wireless communication devices such as mobile phones and wireless local area networks (LAN) (IEEE802.11) have become faster and cheaper.

  Conventionally, wired communication devices have been used in power plants and chemical plants for the purpose of monitoring and controlling equipment. However, the introduction of wireless communication devices as part of the monitoring and control system reduces wiring costs. It has been demanded.

  When wireless communication is used for device monitoring and control, a wireless communication technique represented by Zigbee (registered trademark) or the like capable of multi-hop communication by ad hoc wireless communication may be used.

  On the other hand, wireless LAN (IEEE802.11), which has been developed mainly for Internet connection, reduces the communication error rate by changing the modulation method and error correction coding rate when the transmission state of wireless communication is poor. In addition, the communication throughput can be stabilized. Further, even when an error occurs in communication, the same data can be retransmitted.

  When the radio wave propagation environment for wireless communication deteriorates and retransmissions occur frequently, the communication throughput decreases. To solve this problem, the ratio of retransmission frames is measured based on frames received per unit time, the frame retransmission rate is equal to or higher than a predetermined threshold, and the reception level of the received signal is specified in advance. A technique for selecting a higher data transmission rate for communication when the data transmission rate is equal to or higher than the minimum level is disclosed (for example, see Patent Document 1).

JP 2007-166120 A

  However, the technique described in Patent Document 1 is preliminarily defined in the wireless communication frequency channel when the radio wave propagation environment changes due to movement of people or objects around the wireless communication device and the communication error rate increases. There is a problem that a communication error rate is not sufficiently improved even if any data transmission rate is used, and a necessary throughput cannot be obtained. Specifically, in wireless communication, a frequency channel is generated in which the signal reception level of the wireless communication apparatus is reduced due to the effects of multipath and fading in radio wave propagation.

  On the other hand, depending on the movement situation and arrangement of people and objects, there are frequency channels in which the influence of multipath and fading is relatively small and the reception level is hardly lowered in different frequency channels.

  In such a case, it is possible to improve the communication error rate by changing to a frequency channel with little decrease in reception level, but in general, the frequency channel is commonly set between the transmission device and the reception device. Therefore, after the radio wave propagation environment changes and the communication error rate increases, it is difficult to change the frequency channel by transmitting and receiving communication signals between the transmission device and the reception device.

  The present invention has been made in view of such a background, and the present invention is a wireless communication device that can suppress a decrease in throughput by reducing a communication error rate in a wireless communication path provided between wireless communication devices. An object is to provide a communication device and a wireless communication method.

  In order to solve the above problems, the wireless communication device and the wireless communication method of the present invention measure a communication error rate in a wireless communication path between other wireless communication devices connected to the wireless communication device of the wireless communication device and the wireless communication device. When the communication error rate exceeds a predetermined threshold value, a new frequency channel to be changed is selected in the wireless communication path, and information on the selected new frequency channel is wirelessly different from the wireless communication path. It transmits to another radio | wireless communication apparatus via a communication path | route, and changes the setting of the frequency channel of the said radio | wireless communication path | route to a new frequency channel, It is characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communication apparatus and radio | wireless communication method which suppress the fall of a throughput can be provided by reducing the communication error rate in the radio | wireless communication path | route provided between radio | wireless communication apparatuses.

It is a figure which shows the structure of the communication network system using the radio | wireless communication apparatus which concerns on this embodiment. It is a functional block diagram which shows the structural example of the gateway station (wireless communication apparatus) which concerns on this embodiment. It is a functional block diagram which shows the structural example of the relay station (wireless communication apparatus) which concerns on this embodiment. It is a figure for demonstrating the frequency channel set in a radio | wireless communication apparatus. It is a figure for demonstrating the fluctuation | variation by the frequency of the reception level of a radio | wireless communication signal. It is a figure for demonstrating the outline | summary of the change process of the frequency channel in the radio | wireless communication apparatus which concerns on this embodiment. It is a sequence diagram which shows the flow of the change process of the frequency channel in the radio | wireless communication apparatus which concerns on this embodiment.

  Next, modes for carrying out the present invention (referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.

  FIG. 1 is a diagram illustrating a configuration of a communication network system 100 using a wireless communication apparatus according to the present embodiment. As shown in FIG. 1, the communication network system 100 includes a gateway station 1, a relay station 2 (2A, 2B,..., 2F), a terminal station 3, a hub 4, a control device 5, and a device 6. Consists of including. Note that the wireless communication device in the present application means the gateway station 1, the relay station 2, and the terminal station 3 constituting the wireless communication network among the devices constituting the communication network system 100 shown in FIG. 1. Details will be described later with reference to FIG. 2 and FIG.

The control device 5 monitors or controls the device 6 by the constructed communication network system 100.
The hub 4 is a communication device for enabling communication data to be exchanged with a plurality of devices. Generally, the hub 4 is a switching hub corresponding to Ethernet (registered trademark), a layer 2 switch, a layer Three switches are used. The hub 4 may not be provided when it is not necessary to connect to the external network 7.

  The control device 5 and the hub 4, the external network 7 and the hub 4, the hub 4 and the gateway station 1, and the terminal station 3 and the device 6 are connected by wired communication paths 10 (10a, 10b, 10c, 10d), respectively. The wired communication path 10 is assumed to be connected by a general-purpose communication interface such as Ethernet (registered trademark).

  The gateway station 1 converts physical signals between wired communication and wireless communication, and also uses a wired communication protocol such as Ethernet (registered trademark) and a wireless communication protocol such as wireless LAN (IEEE802.11). Logical protocol conversion between In addition, when a communication packet needs to be transmitted toward a specific address, it also has a router function for determining a communication direction according to the address. The specific configuration of the gateway station 1 will be described in detail with reference to FIG.

The relay station 2 (2A, 2B,..., 2F) is wirelessly connected to the gateway station 1, a relay station 2 other than itself, or the terminal station 3 via a plurality of wireless communication paths 20 (20a, 20b,..., 20k). Send and receive communication signals.
A specific configuration of the relay station 2 will be described in detail with reference to FIG.

The terminal station 3 is connected to the relay station 2 (2E, 2F) via the wireless communication path 20 (20i, 20k) to transmit and receive wireless communication signals, and is also connected to the device via the wired communication path 10 (10d). 6 is connected.
The terminal station 3 has the same function and configuration as the gateway station 1 and converts physical signals between wired communication and wireless communication, and wired communication such as Ethernet (registered trademark). Perform logical protocol conversion between the protocol and a wireless communication protocol such as wireless LAN (IEEE802.11). In addition, when a communication packet needs to be transmitted toward a specific address, a router function for determining a communication direction according to the address is also provided.

  In general, wireless communication has a higher communication error rate and lower reliability than wired communication. Therefore, as shown in FIG. 1, the wireless communication paths 20 constituting the wireless communication network are multiplexed (in mesh type). By configuring), the reliability of communication is enhanced with respect to transmission of information for monitoring or control between the control device 5 and the device 6.

Next, the gateway station 1 (wireless communication apparatus) will be specifically described. FIG. 2 is a functional block diagram illustrating a configuration example of the gateway station 1 according to the present embodiment.
As illustrated in FIG. 2, the gateway station 1 includes a plurality of communication units 11 (11a, 11b, 11c), a control unit 12, and a storage unit 13. Note that the terminal station 3 according to the present embodiment has the same configuration as that of the gateway station 1, and thus the description thereof is omitted.

  The communication unit 11 includes a communication unit 11c including a wired communication IF (interface) unit 114, a wireless communication IF unit 111 (111a, 111b), an error rate measurement unit 112 (112a, 112b), and a frequency conversion unit 113 (113a). , 113b) and communication units 11a, 11b. Note that the gateway station 1 and the terminal station 3 in this embodiment use one or more communication units 11 (for example, the communication unit 11c in FIG. 2) that perform transmission / reception using the wired communication path 10 and the wireless communication path 20. And a plurality of communication units 11 (for example, communication units 11a and 11b in FIG. 2).

The wired communication IF unit 114 and the wireless communication IF unit 111 convert physical signals between wired communication and wireless communication.
The error rate measuring unit 112 measures a communication error rate in communication data transmitted / received through each wireless communication path 20 via each wireless communication IF unit 111.
The frequency conversion unit 113 converts the frequency channel of the wireless communication signal to be transmitted / received into a new frequency channel selected by the communication frequency control unit 122 under the control of the communication frequency control unit 122 in the control unit 12 to be described later. .

The control unit 12 includes a protocol conversion unit 121 and a communication frequency control unit 122.
The control unit 12 is realized by a program execution process or a dedicated circuit by a CPU (Central Processing Unit) included in the gateway station 1, and when realized by the program execution process, the control unit 12 stores the gateway station in the gateway unit 1. A program for realizing one function is stored.

  The protocol conversion unit 121 performs logical protocol conversion between a wired communication protocol such as Ethernet (registered trademark) and a wireless communication protocol such as a wireless LAN (IEEE802.11).

When the communication error rate in the wireless communication path 20 exceeds a predetermined threshold, the communication frequency control unit 122 selects a new frequency channel and creates a new one via the wireless communication path 20 that is different from the wireless communication path 20. Information on the frequency channel is transmitted to the relay station 2. Then, the communication frequency control unit 122 changes the setting of the frequency channel of the wireless communication path 20 whose communication error rate has exceeded a predetermined threshold to a new frequency channel.
The communication frequency control unit 122 includes an error rate determination unit 123, a frequency selection unit 124, a frequency change information transmission / reception unit 125, and a frequency setting unit 126.

  The error rate determination unit 123 acquires information on the communication error rate for each wireless communication path 20 measured by the error rate measurement unit 112, and determines whether the communication error rate exceeds a predetermined threshold.

  The frequency selection unit 124 selects a new frequency channel for the wireless communication path 20 that has been determined by the error rate determination unit 123 that the communication error rate exceeds a predetermined threshold value and that the setting of the frequency channel needs to be changed.

The frequency change information transmission / reception unit 125 transmits the frequency change request information including information on the new frequency channel selected by the frequency selection unit 124 to the radio communication path 20 different from the radio communication path 20 in which the communication error rate exceeds a predetermined threshold. To send through. In addition, frequency change response information is received as a response from another wireless communication device to the frequency change request information.
The frequency change information transmitting / receiving unit 125 includes the functions of the frequency change information transmitting unit and the frequency change information receiving unit described in the claims.

  The frequency setting unit 126 receives an instruction to change the setting to a new frequency channel selected by the frequency selection unit 124 when the frequency change information transmission / reception unit 125 receives frequency change response information from another wireless communication device. This is performed for the frequency conversion unit 113 in the communication unit 11 connected to the wireless communication path 20 in which the error rate exceeds a predetermined threshold, and the setting of the frequency channel is changed.

  The storage unit 13 includes storage means such as a RAM (Random Access Memory) and a cache memory, and temporarily stores information to be transmitted and received.

Next, the relay station 2 will be specifically described. FIG. 3 is a functional block diagram illustrating a configuration example of the relay station 2 according to the present embodiment.
As illustrated in FIG. 3, the relay station 2 includes a plurality of communication units 21, a control unit 22, and a storage unit 23. In addition, the structure which has the same function as the gateway station 1 of FIG. 2 attaches | subjects the same name, and abbreviate | omits description.

The difference from the gateway station 1 shown in FIG. 2 is that there is no communication unit 11c provided with the wired communication IF unit 114 as shown in FIG. 2, and the relay station 2 shown in FIG. It is a point provided with the communication part 21c.
The communication unit 21c includes a wireless communication IF unit 211c, an error rate measurement unit 212c, and a frequency conversion unit 213c having the same functions as the functions of the other communication units 21a and 21b. That is, the relay station 2 in the present embodiment includes a plurality of communication units 21 (21a, 21b, 21c) that perform transmission and reception using the wireless communication path 20.

The setting of the frequency channel by the communication frequency control units 122 and 222 of the gateway station 1 (terminal station 3) and the relay station 2 as the wireless communication devices will be described.
FIG. 4 is a diagram for explaining frequency channels set in the wireless communication apparatus. As shown in FIG. 4, in a frequency band from a certain frequency f1 to a frequency f2, a plurality of frequency channels having a bandwidth fd are provided, and communication is performed using one arbitrarily selected frequency channel (for example, channel 406). For example, when a wireless LAN (IEEE802.11g) is used, 13 frequency channels (frequency channels 401, 402,..., 413) having a 20 MHz width per channel are provided in a 2.4 GHz band frequency.

FIG. 5 is a diagram for explaining the variation of the reception level of the wireless communication signal depending on the frequency.
As shown in FIG. 5, in wireless communication, the reception level value 500 of the wireless communication signal varies depending on the frequency due to the influence of multipath and fading. Since external noise also increases or decreases depending on the frequency, the communication error rate differs depending on which frequency channel is selected for communication.

  However, depending on the movement situation and arrangement of people and things, there are frequency channels that can communicate with a low communication error rate in different frequency channels, so changing to such a frequency channel reduces the communication error rate, A reduction in throughput can be suppressed.

  Next, the flow of processing of the wireless communication method according to the present embodiment will be described using FIGS. 6 and 7 with reference to FIGS.

  FIG. 6 is a diagram for explaining an outline of frequency channel change processing in the wireless communication apparatus (gateway station 1, relay station 2, terminal station 3) according to the present embodiment. In FIG. 6, in order to monitor or control the device 6, the control device 5 transmits and receives information via a wireless communication network configured in a mesh type. Here, since the communication error rate increases between the gateway device 1 (first wireless communication device) and the relay station 2A (second wireless communication device) constituting the wireless communication network and exceeds a predetermined threshold, Description will be made assuming that the frequency channel of the wireless communication path 20a is changed. Even when the communication error rate increases in the wireless communication path 20 between the relay station 2 and another relay station 2 or in the wireless communication path 20 between the relay station 2 and the terminal station 3, it will be described later. The relay station 2 and the terminal station 3 can similarly perform the frequency channel changing process described below.

  In FIG. 6, the gateway station 1 detects that the communication error rate has increased in the wireless communication path 20a between the gateway station 1 and the relay station 2A. When the communication error rate exceeds a predetermined threshold, the gateway station 1 transmits frequency change request information including information on a new frequency channel to be changed to the relay station 2A via the relay station 2B. (Reference numerals 30a and 30b).

  The relay station 2A that has received the frequency change request information via the relay station 2B changes the setting to a new frequency channel included in the frequency change request information. Then, the relay station 2A transmits frequency change response information indicating that the setting has been changed to a new frequency channel to the gateway station 1 via the relay station 2B (reference numerals 31a and 31b).

  The gateway station 1 that has received the frequency change response information from the relay station 2A via the relay station 2B changes the setting of the radio communication path 20a to a new frequency channel, and transmits / receives data to / from the relay station 2A.

  Next, frequency channel change processing in the wireless communication apparatus will be specifically described. FIG. 7 is a sequence diagram showing a flow of frequency channel change processing in the wireless communication apparatus according to the present embodiment. In FIG. 7, as in FIG. 6, the communication error rate between the gateway device 1 (first wireless communication device) and the relay station 2A (second wireless communication device) increases and exceeds a predetermined threshold. A description will be given assuming that the setting of the frequency channel of the wireless communication path 20a is changed (see FIGS. 2 and 3 as appropriate).

  First, the error rate measuring unit 112a (see FIG. 2) of the gateway device 1 measures the communication error rate with the relay device 2A (step S701). Here, it is assumed that the communication unit 11a of the gateway station 1 and the communication unit 21a of the relay station 2A are connected via the wireless communication path 20a and perform data communication.

  Subsequently, the error rate measurement unit 112 a sends information related to the communication error rate, which is the measurement result, to the communication frequency control unit 122. Then, the error rate determination unit 123 of the communication frequency control unit 122 determines whether or not the communication error rate exceeds a predetermined threshold (step S702). If the error rate determination unit 123 determines that the communication error rate does not exceed a predetermined threshold (step S702 → No), the process returns to step S701 to continue the processing. On the other hand, when the error rate determination unit 123 determines that the communication error rate exceeds a predetermined threshold (step S702 → Yes), the process proceeds to the next step S703.

  In step 703, the frequency selection unit 124 of the communication frequency control unit 122 selects a new frequency channel in order to change the setting of the currently communicating frequency channel.

  Then, the frequency change information transmission / reception unit 125 transmits the frequency change request information including information on the new frequency channel selected by the frequency selection unit 124 via the relay station 2B via the communication unit 11b (see FIG. 2). It transmits to 2A (step S704).

  Next, in the relay station 2A, the frequency change information transmitting / receiving unit 225 of the communication frequency control unit 222 receives the frequency change request information via the communication unit 21b (see FIG. 3) (step S705). Then, the frequency setting unit 226 sends an instruction to change the setting to a new frequency channel specified by the received frequency change request information to the frequency conversion unit 213a, and changes the setting of the frequency channel for the wireless communication path 20a (step S706). ).

  Subsequently, the frequency change information transmitting / receiving unit 225 of the relay station 2A sends the frequency change response information, which is information indicating that the setting has been changed to a new frequency channel, to the gateway station via the relay station 2B via the communication unit 21b. 1 is transmitted (step S707).

  In the gateway station 1, the frequency change information transmitting / receiving unit 125 receives the frequency change response information via the communication unit 11b (see FIG. 2) (step S708).

  Next, the frequency setting unit 126 of the gateway station 1 sends an instruction to change the setting to the new frequency channel selected by the frequency selection unit 124 to the frequency changing unit 113a, and changes the setting of the frequency channel for the wireless communication path 20a. (Step S709).

  By doing in this way, in the wireless communication apparatus (gateway station 1, relay station 2, terminal station 3) and the wireless communication method according to the present embodiment, the communication error rate of the wireless communication path 20 for transmitting and receiving data is predetermined. When the threshold value is exceeded, a new frequency channel can be selected and information regarding the new frequency channel can be transmitted via different wireless communication paths 20. Then, by changing the setting of the radio communication path 20 to a new frequency channel, the communication error rate can be reduced and the reduction in throughput can be suppressed.

1 Gateway station (wireless communication equipment)
2 Relay station (wireless communication device)
3 Terminal station (wireless communication device)
4 Hub 5 Control device 6 Device 7 External network 10 Wired communication path 11, 21 Communication unit 12, 22 Control unit 13, 23 Storage unit 20 Wireless communication path 100 Communication network system 111, 211 Wireless communication IF unit 112, 212 Error rate measurement Units 113 and 213 Frequency conversion unit 114 Wired communication IF unit 121 and 221 Protocol conversion unit 122 and 222 Communication frequency control unit 123 and 223 Error rate determination unit 124 and 224 Frequency selection unit 125 and 225 Frequency change information transmission / reception unit 126 and 226 Frequency Setting section

Claims (4)

The wireless communication device used in a communication network system in which a wireless communication path provided between a plurality of wireless communication devices is configured in a mesh type to perform data communication,
Measure a communication error rate in the wireless communication path with another wireless communication device connected to its own wireless communication device, and when the measured communication error rate exceeds a predetermined threshold, the wireless communication route A new frequency channel to be changed is transmitted, and information on the selected new frequency channel is transmitted to the other wireless communication device via a wireless communication path different from the wireless communication path, and the wireless A radio communication apparatus, wherein a frequency channel of a communication path is changed to the new frequency channel. The wireless communication device used in a communication network system in which a wireless communication path provided between a plurality of wireless communication devices is configured in a mesh type to perform data communication,
An error rate measurement unit that measures a communication error rate in the wireless communication path between the wireless communication device and another wireless communication device connected to the wireless communication device;
An error rate determination unit that determines whether the communication error rate measured by the error rate measurement unit exceeds a predetermined threshold; and
When the error rate determination unit determines that the communication error rate exceeds a predetermined threshold, a frequency selection unit that selects a new frequency channel to be changed in the wireless communication path; and
A frequency change information transmitting unit for transmitting frequency change request information including information on the new frequency channel selected by the frequency selecting unit to the other wireless communication device via a wireless communication path different from the wireless communication path; ,
Frequency change response information, which is information indicating that the frequency channel of the wireless communication path is changed to the new frequency channel based on the frequency change request information, is different from the wireless communication path from the other wireless communication device. A frequency change information receiving unit for receiving via a wireless communication path;
Triggered by the frequency change information receiving unit receiving the frequency change response information, a frequency setting unit that changes the frequency channel of the wireless communication path to the new frequency channel selected by the frequency selection unit;
A wireless communication apparatus comprising:   The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus includes a plurality of wireless communication interfaces for transmitting and receiving data using the plurality of wireless communication paths. A wireless communication method used in a communication network system in which a wireless communication path provided between a plurality of wireless communication devices is configured in a mesh type to perform data communication,
When the first wireless communication device and the second wireless communication device perform data communication through the wireless communication path,
The first wireless communication device is:
Measuring a communication error rate in the wireless communication path between the first wireless communication device and the second wireless communication device;
Determining whether the measured communication error rate exceeds a predetermined threshold;
In the determination, if the communication error rate exceeds a predetermined threshold, selecting a new frequency channel to change the setting in the wireless communication path;
Transmitting frequency change request information including information on the selected new frequency channel to the second wireless communication device via a wireless communication path different from the wireless communication path; and
The second wireless communication device is:
Receiving the frequency change request information from the first wireless communication device;
Based on the received frequency change request information, changing the setting of the frequency channel of the wireless communication path to the new frequency channel;
Transmitting frequency change response information, which is information indicating that the setting has been changed to the new frequency channel, to the first wireless communication device via a wireless communication path different from the wireless communication path; ,
The first wireless communication device is:
Receiving the frequency change response information from the second wireless communication device;
And a step of changing the setting of the frequency channel of the wireless communication path to the new frequency channel in response to the reception of the frequency change response information.

Images